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Saturday, February 23, 2008

I’ve had many people ask me, “Why are there so few birds at my feeder this winter?” The short answer is, “I don’t know.”

I don’t have many birds at my feeders either. Through the Fall and early Winter, my feeders were teeming with birds. There were large flocks of finches and sparrows. Common Redpolls were a highlight of the early winter, with a flock of fifty or more feeding throughout the day. Now they are gone. What’s happened?

Before I continue, let me remind readers that I am a birding hobbyist. I am not a scientist. Early in my academic career, I was a major in science and acquired an understanding of how science does its research, weighs its evidence, tests its theory, and arrives at the “facts” based on the best evidence available at the moment. At its best, science relies on empirical data and the research of one scientist can be verified by another scientist. Conclusions are based upon research, not political positions, economic theory, or theological bias - such as those which try to influence a lot of science in our current society.

I may have begun with the study of science, but I swerved into history, and we all know how historians can interpret and reinterpret historical events. There is nothing precise about the writing of history.

Nevertheless, I do try to get the science right as I write about birds. So a disclaimer: I do not know any science about why there are so few birds coming to my bird feeders during the last couple of months. Nor do I know why there are so few birds coming to some other people’s bird feeders.

I also don’t know if the lack of birds at my bird feeders is typical. There are a lot of anecdotal reports to suggest that the reality is complex.

For example: Common Redpolls. I was enthralled with the flock that came to my feeders in the early winter. Then they disappeared. Since the beginning of the year, a single redpoll has come to the feeders a couple of times, spending a day or two, and then disappearing. But a friend atop Newfane Hill announced that a flock of two hundred redpolls were busy around her homestead. And a conversation about bird feeders with a Dummerston resident included many redpolls.

On the last day of the old year, I wrote about the cardinals which came daily to my feeders - Prince Cardinal with his harem of four. Soon after, they disappeared. Occasionally I would see a single male at dusk, or a single female at some other time of the day. But the tiny group was gone. Had the repeated winter storms done them in? Or had they moved southward, trying to avoid the brunt of winter? Unanswered and unanswerable questions?

Last Sunday, cardinals were back at the feeders - Prince Cardinal and at least three females. The same ones as earlier in the winter? Probably, since cardinals are not known to migrate. If so, where have they been? There is always plenty of seed at my feeders, and we clear the snow and ice at least once a day. Had they gone to someone else’s feeders? Had they found another source of high energy food in a place more protected from the elements? I don’t know.

A similar thing happened with other wintering birds. For several weeks, I had only one or two stray chickadees and a single Downy Woodpecker; their feeder visits were brief and erratic. Then the “normal” neighborhood flock returned - several chickadees and titmice, a couple of nuthatches, a pair of Downy Woodpeckers, and a Hairy Woodpecker. In winter, these year round residents forage in mixed flocks and can be nomadic. Apparently, their nomadism has brought them back to my yard.

As many people who have queried me about the absence of birds at their feeders, just as many are unaware of any problem. They have plenty of birds at their feeders - or at least a respectable number. Sighting reports from southeastern Vermont and around the state continue to report wintering northern birds, often in substantial numbers (Pine Grosbeaks, Snow Buntings, Horned Larks, redpolls). Last week I saw a large flock of Evening Grosbeaks in Guilford getting grit and salt from the road, along with doves, robins, and juncos - none of which have been in my neighborhood for weeks.

In spite of the continuing grip of winter, some birds are already on the move. Reports of Rusty Blackbirds have come from a several places. And last Sunday, a caller reported four male Red-winged Blackbirds at her home on Upper Dummerston Road. The red-wings usually begin appearing during the first week of March.

Two weeks ago, I drove to Philadelphia. I left my home with snow squalls swirling. At the Massachusetts border, the squalls were so heavy that it was almost white-out conditions and I considered turning around. By the time I reached Holyoke, the road was dry, the sun was shining, and there wasn’t a white patch to be seen on the ground anywhere. Which leads me to theorize that many birds which we might expect to see, such as finches and some sparrows, have moved southward to where the foraging is a little easier.

It has been a difficult winter. Even people who enjoy winter are getting tired of it. I know several families who enjoy winter sports, but they are not planning on spending the next week’s winter school break skiing or snowshoeing - they’re going to Florida. I’m tempted to make a comment about people who “wimp out,” but the truth is, I wouldn’t mind wimping out with them.

If many birds have moved south, who can blame them. It has been a tough winter, all the more difficult for those creatures which must make their living in this weather. If there are not as many birds at some feeders this winter, it may mean that they have gone south, or it may mean that they have not survived.

Here is a report that has surprised me. Two people have told me about having a Barred Owl at their feeders. In both case, the owl perched on or very close to the feeder. One of them was clearly observed hunting for rodents. Beneath the snow pack there is lots of life and activity. We’ll see the trails and tunnels when it finally melts. I see red squirrels diving into a hole in the snow and reemerging from another hole ten or twenty feet away. The Barred Owls, whose weak talons restrict their prey primarily to small rodents, were coming to where the mice and voles could be easily found. The owls can hear the mice active beneath the snow pack, but how do they break through the ice crust on top? One observer watched the owl as it tried to plunge through the ice crust, and even tried to scratch and break the surface.

Curiously, neither of these owls was harassed by the small birds. They were ignored. Even the Blue Jays payed no mind to the owl.

Are the numbers of birds more or less than usual this winter? I don’t know. Perhaps data from the Great Backyard Bird Count will tell us. What can be said is that winter is a time of harsh gleaning. In nature, there is no sentiment, or sentimentality, for the weak. The strong and the fit survive.

Saturday, February 16, 2008

An apology ... sort of. Every so often someone will excitedly call me or e-mail me: “Did you see the swans!?” I can seldom respond with any enthusiasm. Because - the swans that are being reported are usually Mute Swans, and unfortunately the presence of Mute Swans is not good news.

Mute Swans are elegant birds - luxuriant pure white plumage, long sinuous necks, graceful swimmers. But they are not native to North America, and like other introduced birds, they pose a threat to native species.

World-wide, there are seven members of Genus Cygnus (from the Latin for swan, coming from the Greek kyknos, also meaning swan), although typical of taxonomic classifications, there is debate whether some subspecies should be accorded their own species status.

Two swans are native to North America. The Trumpeter Swan, the largest native waterfowl in North America, has been returned from the brink of extinction and is being reintroduced in many parts of its former breeding range in Minnesota, Wisconsin, Michigan, and Ontario. There are no recent records of the Trumpeter Swan in Vermont.

The Tundra Swan is our smallest swan, short-necked and gooselike. It nests on the Arctic tundra and migrates to wintering grounds. Many winter along the mid-Atlantic coast. A few may be seen in Vermont during Spring or Fall migration. Most recently, in November 2003 and 2004 Tundra Swans stopped briefly in the Retreat Meadows. The bill of the Tundra Swan is black.

The adult Mute Swan is most readily identified by its unique orange bill and the black mask with forehead knob.

In the last few years, the Mute Swan has become the swan most likely to be seen in southeastern Vermont. Last year a pair nested in the vicinity of the Hinsdale setbacks. To my knowledge, this was the first successful nesting in our area. Murin and Pfeiffer in Birdwatching in Vermont, report that the Mute Swan has “nested in Vermont but the Vermont Fish and Wildlife Department probably won’t allow a repeat performance.”

So, what’s the problem? First, some background. The Mute Swan is native to Europe and western Asia. Its nature and character (elegant, aggressive, silent) made it the subject of many myths and legends. Occasionally it was domesticated for food. More often it was kept as an ornament in the gardens of the nobility beginning at least as early as classical times. The Mute Swan is the national bird of the Kingdom of Denmark, while in Britain, the Crown retains the right to ownership of all unmarked mute swans in open water. Magnanimously, the Queen only exercises her ownership on certain stretches of the Thames and its surrounding tributaries. Swans continue to be a feature in the public parks of Europe.

In the 1800s, many growing American cities expressed their civic pride through the creation of public gardens, complete with paths and ponds. The ponds were decorated with Mute Swans brought from Europe, their wings clipped to keep them in the parks. The pampered swans enjoyed an easy life, settled down and raised families. Naturally long lived (nineteen years is the record for a banded wild swan - thirty to forty years is not uncommon for captive swans) swans often outlived the ponds and estates which kept them. They, or their offspring, went wild. With a high reproductive rate, a lack of natural predators, and an abundance of suitable wetland habitat, these feral Mute Swans have established significant populations, especially along the Atlantic Coast.

A survey conducted in the summer of 2002 found over 14,000 Mute Swans in the Atlantic Flyway. This number had doubled in just sixteen years. The pair that nested in Hinsdale on the Connecticut River last summer raised five young. About fifty swans are wintering in the Turners Falls area. As recently as ten years ago when I moved to southeastern Vermont, Mute Swans were a rare occurrence.

The growth of the Mute Swan population causes several ecological problems. They have voracious appetites and often are a year-round presence. They are capable of disrupting the natural food chain. “Several studies have documented large reductions in aquatic vegetation, and even the complete disappearance of certain plant species in some locales, because of heavy grazing by mute swans. In some areas of the Chesapeake Bay, efforts to restore native vegetation have been seriously hampered by foraging mute swans. In turn, there is a negative impact on native wildlife and fish species that depend on these plants for food and cover.”

During breeding season, Mute Swans maintain a four to ten acre territory, aggressively driving off any intruders, including native species attempting to nest. They have caused terns and skimmers to abandon their nests and have killed Mallard ducklings and goose goslings. Their aggressiveness is sometimes directed toward other animals and even humans. They can be, at the least, a nuisance to pets and people, and perhaps even a danger.

“Adults are not paired for life, contrary to the stereotype of the ‘pining swan’ who has lost its mate. In fact, some have been observed to have as many as four mates, or even ‘divorce’ one mate in favor of another. However, established pairs are more successful breeders than non-established pairs and mute swans do form monogamous pairs for at least a season.”

Ironically, Mute Swans seem to be the only effective control on Canada Geese nesting in many areas, but any benefit derived from limiting the goose numbers is outweighed by the damage the swans cause to aquatic vegetation. On the other hand, their need for a large territory directly competes with the Common Loon, which also needs a sizeable nesting territory. As the native Trumpeter Swan continues its recovery, it may also find itself competing with the Mute Swan for nesting territory.

In the interest of being as fair to the Mute Swan as possible, there is some evidence that it may have been, and therefore may still be, an occasional vagrant to North America. In 1585, while on a scientific exploration to America for Sir Walter Raleigh, John White painted a watercolor which he titled simply, “The Swann.” In the 1960s the British Museum labeled it as a Trumpeter Swan,” probably because its bill is black. However, scientists at the British Museum “say that lead in the paint used by White has degraded over the four hundred years, turning some colors grey or black. The curved neck, the knob, the lifted rear feathers, the entire countenance are consistent with Mute Swan. Research on the painting continues, as does debate as to whether the Mute Swan might have, or could today, occur naturally in North America.

One person’s good bird is often another person’s invasive pest. Good birding is sometimes a messy affair.

Quotations are from the web site of Pennsylvania Game Commission and from wikipedia.org.

Saturday, February 09, 2008

I attended a Short-eared Owl show. I was told that the show began in the early morning, but I did not join the show until two in the afternoon. I watched it until sunset.

When I pulled into the parking area, four people were staring across the barren salt marsh. Short-eared Owl, they told me. Across the ice and snow and broken grasses of the marsh, I saw a dark anomaly. With binoculars I saw the owl’s flat round facial disk. It was still there when I set up my scope and brought it closer with the long lens. It was eating. Then it took flight. In its beak it carried something limp and gray, probably a vole.

The flight was short and when it landed, it resumed its meal. The final remains of its prey disappeared in a single gulp. Then it flew to a stake and perched. From there it surveyed the lifeless looking marsh. Soon it would hunt again.

I wandered slowly, back and forth, along a mile and a half of the Parker River refuge road on Plum Island. Three Short-eared Owls were active along this short stretch. They provided a textbook study of this particular owl, and of life in a winter salt-marsh.

The winter salt-marsh never ceases to amaze me. It is a stark, forbidding landscape. The ponds are frozen. The tidal channels are rimmed with jagged chunks of ice. The reeds and grasses are battered, broken, flattened. Nothing breaks the wind as it sweeps across the open marsh, and the wind, laden with ocean moisture, penetrates. The heavy dampness chills. The winter salt-marsh is not a welcoming place. Forbidding is an appropriate adjective.

And yet ... there is life that goes on about the business of earning its living. In the tidal channels, Red-breasted and Hooded Mergansers dove. The drakes displayed for the hens. Gulls were in constant movement; often one could be seen dropping a mussel, using the hard ice to crack open the shell. Black ducks and geese grazed among the grasses. Robins went from berry bush to berry bush, feeding on the fermented fruit. A mockingbird, his mimicking song still silenced by winter, eyed me with interest and curiosity.

I could easily understand where these birds were finding their food, although I wondered why they might not find a more temperate place to winter.

But consider the birds of prey. In addition to the three Short-eared Owls, I saw at least six Northern Harriers hunting over the marshes and dunes. Somewhere in the large expanse of the refuge, there were wintering Rough-legged and Red-tailed Hawks and at least one Snowy Owl. I did not see them, but there were almost daily reports of their presence. Small rodents make up most of the winter diet of these predators. These raptors may be adapted and accustomed to frigid conditions, but their survival still requires many calories every day. Each of these predators must hunt successfully several times each day.

The owls I watched were consistently successful. The Short-eared Owl is a bird of open spaces - tundra, marshes, grasslands. It is also the owl most likely to be seen hunting in daylight. Owls rely heavily on sound to find their prey. The circular facial disc of the Short-eared Owl acts like a dish receiver, capturing sound and funneling it to the ears. The ear openings are asymmetrical, allowing the owl to triangulate sound and locate its prey. The “short ears” of the Short-eared Owl are not ears, but small feather tufts which are not usually visible.

During the afternoon I watched the Short-eared Owl show. I saw it perch on the ground, camouflaged among the marsh grasses until suddenly it spread its wings for a short flight, landing on prey. Other times it perched on a stake, quite prominent on its elevated position. Its head turned one way, and the other. Then it was still, focused; it took flight - a short flight - landing on prey hidden beneath the snow and matted grasses.

More commonly the Short-eared Owls hunted in flight, climbing and descending, floating nimbly over the marsh. At times they resembled the Northern Harrier , their wings held in a droopy dihedral, but quicker than the harrier. The harrier is a somewhat owl-like hawk with a facial disk to help it hunt by sound; in flight the harrier long and rangy. By contrast, the Short-eared Owl looks like a blunt battering ram, or as Pete Dunne puts it: “a pale beer keg on wings.”

The owls and the harriers did not share the air space willingly. There were frequent aerial dogfights between the Short-eared Owl and the Northern Harrier. Sometimes it looked to me as though the owl was the aggressor, as though it was protecting its exclusive hunting preserve. Other times the harrier made the first aggressive maneuver.

The owl, flying above the harrier, dove and swirled. The harrier rolled on its back, talons up as though protecting itself. But such aerial maneuvers are quick and the purpose not always apparent. I spoke with a photographer who had been watching and photographing the birds all day. He showed me an image where the harrier had rolled in flight onto its back. Visible also was the vole which the harrier had dislodged from the owl’s talons. He described the harrier following the vole to the ground, grabbing it, and flying off. One predator had stolen from another. It is no wonder that predators are often aggressive toward one another.

Hawks usually sit in the open and consume their prey slowly. Owls, on the other hand, try to avoid thieving competitors by swallowing their prey whole. Their digestive system then compacts the indigestible materials (fur and bones) into a pellet. An owl ejects one or two pellets each day. Beneath an owl’s favorite roosting spot there may be a pile of pellets. These pellets have been used by biologists to study diet and foraging patterns.

Like all predators, the Short-eared Owl will take what is available, and this may include a variety of small birds. But its distinct preference is for small mammals. Generally non-migratory, they nevertheless wander, usually in winter, to where the food sources are. When rodent populations explode, the Short-eared Owls somehow get the message and congregate. They have been credited with preventing significant agricultural losses from rodents.

Short-eared Owls are found on every continent except Australia. They have even found their way to the most remote islands on the planet, the Hawaiian Islands, where “Pueo” was worshiped as a god and guardian spirit. On a couple of occasions, I saw a Short-eared Owl hunting on the grassy slopes near the summit of Haleakala on Maui.

It is a curiosity to me that the diurnal raptors, the day-hunting hawks, eagles, and falcons, are often elusive and difficult to study. I see lots of hawks during the Fall migration on Putney mountain, but most are here-and-gone observations. On the other hand, the nocturnal owls have provided a number of extended and rewarding occasions. One of these was the show put on by three Short-eared Owls. They hunted from the ground, a perch, or in the air. They competed with harriers. They swallowed their prey in a single gulp.

The owls reminded me that the winter marsh may appear cold and lifeless. But it is alive with the struggles for survival - with the rhythm of death and of life. At fading light, I was cold, yet conscious that sometimes harsh conditions are necessary for good birding.